Analysis and Design of High Gain NRI Superstrate Based Antenna for RF Energy Harvesting System

Abstract

A high gain patch antenna inspired by 4 layers of negative refractive index (NRI) metamaterial superstrate is proposed to operate at downlink radio frequency (RF) band (935 MHz to 960 MHz of GSM 900). The metamaterial unit cell consists of a nested split ring resonator (SRR) and strip line laminated on other side of FR4 substrate. The effective permittivity and permeability of the proposed unit cell are designed synchronously to approach zero, which leads the NRI superstrate to have impedance match with zero and negative refractive index.The NRI superstrate is studied using Fabry-Perot (F-P) resonant cavity. The gain is improved by 82.48% at the air gap of 55 mm in the desired frequency band.Therefore, the gain of the antenna is effectively enhanced based on the negative refractive index metamaterial. The measured radiation pattern and S parameter results also showed that it has good agreement with the simulation results.